>>1978226Google tells me old 8- and 9-speed have the same pull ratio so they're compatible. However post 2001 they changed things up for 9-speed.
I'm not 100% sure where exactly your rd falls but apparently you can tell the pull ratio by the position of the b screw. Old Campagnolo derailleurs have it directly at the mounting point, yours with the screw on the cage (picrel) would be the new pull-ratio. The b screw is the thing I previously told you to adjust to set the distance to the cassette.
So that rd wont work as far as I'm concerned.
I guess you learn something new every day.